OK I'll give it a go. 4 small set screws hold the upper and lower together, loosen the screws and slide the uppers apart. The tabs on the upper will align with the slots in the lower and they will separate.
Undo the 4 Allen head screws in the side of the lower that hold the barrel clamp, remove clamp from lower guard, remove the 1 cap screw from the barrel clamp and it will hinge open.
Install the clamp around the barrel with the upright tabs forward (?looks to me anyway) install capscrew and snug it a little, slide lower on and install loosely 4 Allen head bolts in side of lower into the barrel clamp and install the large screw that came out of the wood lower hand guard rear bottom
Drop upper guard into slots on the lower and slide rearward, spring loaded pin should be towards the front and now in the gas adjuster detents, install the 4 setscrews upwards through the bottom handguard and snug them up.
Check everything looks/aligns good and you can tighten everything, the capscrew securing the barrel clamp can be accessed through the rail so it can be tightened with everything installed.
Seems the barrel clamp will work either way (after playing with it) but with the tabs to the front it looks like it would prevent the gas adjustment from over rotating.
I did the best I can with pics so I hope they are good enough.
